0.2.4 fixes

Squashed commit of the following:

commit 1d719ab07ebf7604efe5bdc131c9b85a146f2303
Author: Arne Claassen <arne@claassen.net>
Date:   Mon Jan 14 10:31:40 2013 -0800

    more completion work, and discovered some readline handler omissions

commit 531ba4149305446f70ae8e0529f24485c017fd53
Author: Arne Claassen <arne@claassen.net>
Date:   Mon Jan 14 10:20:29 2013 -0800

    wip on fixing path completions

commit a26daf296005072d5f979cc6017872e4a0ea9a1a
Merge: eef5195 34be423
Author: Arne Claassen <arne@claassen.net>
Date:   Sun Jan 13 15:18:59 2013 -0800

    Merge branch 'master' into dev

commit eef51956957216d6945e7791057573cde35f0277
Author: Arne Claassen <arne@claassen.net>
Date:   Sun Jan 13 14:41:56 2013 -0800

    removed _exec and made _default do it all

commit 56c88d504b07d7769db6d2368d6603cc775d42a4
Author: Arne Claassen <arne@claassen.net>
Date:   Sun Jan 13 14:15:26 2013 -0800

    re-vamping how default/exec handling is done
Merge branch 'master' into dev
- added supported key bindings for readline to README
- added hook for C-l so shell clear command can be triggered by it
- fixed word forward/back logic to consider only alphanumeric as word
  chars, and extracted logic for this so it can be used for word deletes